When I first started folks mentioned carrying a clipboard to "look official" so as to ward off muggle attention. That sounded good but I use something a little smaller and more convenient. It's a small spiral bound pocket notebook. You can flip it open and lay the GPS over or under it if need be. It cammos the GPS hand well.I have used this one many times. I always have a mini-composition book in the van for notes while driving too. Now that I came across one really cheap, I have started to carry an orange vest and a hard hat just in case I need to look even more 'official' than just the clipboard.
JustJohn - I like to wear the Mechanix brand gloves when reaching into nooks and crannies, and when climbing (coral outcroppings are sharp).
Nobody mentioned it, and it may be a no-brainer, but I carry plenty of ziplock bags, and used plastic grocery bags for trash and such.